**there is NO LEGAL ADOPTION in Islam as we define an adoption in the west. a muslim can be a guardian and provide whatever he/she wants to but can NOT give him ur name and ur inheritence and this is to protect the rights of inheritence of their own children and next of kin. there is a list of relations who inherit a dead man's assets of the deceased.
for example, in the absence of any children, parents inherit, in their absence brothers/sisters get the inheritence and if they are NOT there then nephews and neices...and so on so forth.
even in the west, the confidentiality law is challenged in courts. the adopted children have the right to know who their biological parents are.**
but to be the 'guardian' you have to go through the same process, so while the specifics may be different and in islam this taking care of children is more like fostering than adopting but if we look at the process, it is the same, you may not give your last name to the kid, you may not give him inheritance, however the paperwork you have to do is exactly the same to bring an orphan or abandoned child into your home and raise him or her.
and a muslim can by all means give inheritance to this child, they can give it as a gift, there is no limit on what they can give as a gift to their child, the living or posthumous discussion then gets played out, but the shariah defined beneficiaries can gift their share to the child.
as far as name goes, you can give your last name to the kid, what you cant do is keep the adoption a secret. many kids have no names, you dont know what the parents names of some abandoned kids were anyways, so any name can be given, and to keep all kids of paperwork sorted, them having your last name is no issue.
the children have a right to know who their birth parents are...if it is known. most of the time it is not known.
plenty of discussions on this topic with all kinds of things like mehram, inheritance, name and other factors thrown about. at the end of the day, you can not claim that they are your biological children, the fact that they are adopted should be known, which btw is in line with what most experts in adoption issues recommend anyways. everything else is really a nonfactor for all practical considerations
PS: the inheritance laws were stated as such so ppl dont discourage adoption because they feel this outsider is going to take away from their part of the loot after the parent kicks the bucket. however some common sense and civility needs to prevail. I have noted the case of a couple who was friends with my sis and bro in law, the adopted a girl and later died in an accident, well, the dude's brothers took over all the property and assets and booted the toddler to the curb. 100% legal by shariah right? where did the humanity go. think about it, is that really what god wants anyone to do to an orphan?
PS2: the inheritance laws were also to protect them from predators, to avoid ppl 'adopting' orphans left behind by some rich couple just to get their hands on what rightfully belongs to the child, so lets complete the picture when we start stating islamic inheritancet laws and why and whats of them
s some rich couple dies and