Daughters-in-law which your “adopted son” has divorce are eligible to an “adoptive father”. The precedent was set by the Prophet himself. God’s Messenger walked in on his daughter-in-law Zaynab when she was almost naked and he just had to have her. His adopted son divorced her so that the man he considered his father could marry her. A revelations concerning the “righteousness” of the whole thing followed by revelations confirming that the Prophet was in no way at fault.
33:37 And [remember] when you said to him whom Allah favoured and you favoured: (this is addressed to Zayd regarding his wife Zaynab) “Hold on to your wife and fear Allah”, while you concealed within yourself what Allah would reveal and feared other men, whereas Allah had a better right to be feared by you. Then, when Zayd had satisfied his desire for her, We gave her to you in marriage; so that the believers should not be at fault, regarding the wives of their adopted sons, once they have satisfied their desire for them. For Allah’s Command must be accomplished.
33:38 The Prophet was not at fault regarding what Allah prescribed for him as was His Way with those who were gone before. And Allah’s Command is a pre-ordained decree.
33:39 Those who were delivering Allah’s Messages and feared Him, fearing none other than Allah. Allah suffices as a Reckoner.
Widows must wait four months and ten days before seeking a replacement for a deceased spouse. During this time, they must not be seen in the company of men and must refrain from doing anything that would attract the attention of eligible suitors.
2:234 As for those of you who die leaving wives behind, their wives should observe a waiting period (during this period, they should stay away from men) of four months and ten days. When they have completed that period you incur no offence on account of what they may do with themselves (such as adorning themselves or looking out for suitors) in a lawful manner. Allah has knowledge of what you do.
A man may, however, communicate to a widow, during the waiting period, his interest in making her his wife once the waiting period is over.
2:235 You incur no offence by disclosing your marriage proposals to women or by concealing them; Allah knows that you will remember them. And do not arrange anything secretly with them unless you speak what is recognized as true; and do not resolve on contracting the marriage until the prescribed period (the waiting period) ends. And know that Allah knows what you have in mind, and that Allah is Forgiving, Clement.
Can a man obtain a widow as an inheritance? Not against her will.
4:19 O believers, it is not lawful for you to inherit the women [of deceased kinsmen] against their will; nor restrain them in order to take away part of what you had given them, unless they commit flagrant adultery. Associate with them kindly; and if you feel aversion towards them, it may well be that you will be averse to something, from which Allah brings out a lot of good.
What about trading one wife for another? Yes, but don’t ask for your money back.
4:20 If you wish to have one wife in the place of another and you have given either of them a heap of gold, do not take any of it back. Would you take it by recourse to injustice and manifest sin?
4:21 For how can you take it back, when you have been intimate one with the other, and they had taken from you a solemn pledge?
In Islam, if a problem, real or imagine, involves a female and it has nothing to do with her having sex outside marriage, than marriage is most often the solution. Marriage is also Allah’s recommended course of action in dealing with female orphans.
As you consider the following scattered noble sentiments concerning orphans, keep in mind that the male guardian of female orphans could, at his discretion, “marry such of the women as appeal to” him when they reached the age of nine (the age at which females can be married off under Islamic law i.e. the Sharia). By doing so, he maintains effective control of whatever property the female orphan might possess to use and dispose of at his discretion.
4:2 Render unto the orphans their property and do not exchange worthless things for good ones, and do not devour their property together with your property. That indeed is a great sin!
4:3 If you fear that you cannot deal justly with the orphans, then marry such of the women as appeal to you, two, three or four; but if you fear that you cannot be equitable, then only one, or what your right hands own (captives of war or slave-girls). That is more likely to enable you to avoid unfairness.
4:4 And give women their dowries as a free gift, but if they chose to give you anything of it, then consume it with enjoyment and pleasure.
4:5 But do not give the feeble-minded the property that Allah assigned to you as a means of livelihood. Provide for them therefrom, clothe them and speak kindly to them.
4:6 Test the orphans until they reach the age of marriage; then, if you discern in them sound judgement, deliver to them their property; and do not consume it extravagantly and hastily before they come of age. He who is rich should be abstinent, and he who is poor, should consume fairly. And when you deliver to them their property, call in witnesses thereon. God suffices as a Reckoner!
4:9 And let those who worry about the weak offspring they may leave behind them (after their death) be mindful [of the orphans]. Let them fear Allah and speak justly.
4:10 Those who devour the property of orphans unjustly, devour fire in their bellies, and they will burn in a blazing fire.
4:127 They consult you concerning women. Say: “Allah has instructed you concerning them, and concerning what is recited to you in the Book regarding orphan women for whom you do not give what is prescribed for them, although you wish to marry them, and concerning the weak children, and your duty to deal justly with the orphans (when considering the dowry and inheritance). For whatever good you do, Allah knows it very well.”