It is not permissible to name the orphan after your husband for the purpose of sponsoring him
Question

                I got married six years ago and I do not have children yet. I was dreaming before I got married to sponsor an orphan and feed him as well as I feed my son, and to bring him up with my son, so that I may win the close place of the prophet (PBUH) in paradise.
The suitable chance for sponsoring an orphan did not become available but now, while my brother’s wife is pregnant, she is also my husband’s sister. So that she feeds the orphan with her son, this will make the orphan mahram for me and to my husband and the family. I thought of prohibition of adopting, but I live in a gulf country, and the residency law does not allow us to have any child with us unless he has our name.
I would like to ask about the ruling on adopting in presence of all these barriers? Knowing that both my family and my husband’s family know that we will adopt a child.
Praise be to Allah.Firstly: 
We ask Allaah to bless you with righteous offspring who will bring you joy and will help you to obey Allaah and please Him. 
Secondly: 
Sponsoring an orphan is one of the greatest acts of worship, because of the immense reward that it brings and because of the compassion, kindness and care of the orphan that is involved. 
As for adoption, it is clearly haraam, because Allaah says (interpretation of the meaning):  
“nor has He made your adopted sons your real sons. That is but your saying with your mouths. But Allaah says the truth, and He guides to the (Right) Way.
5. Call them (adopted sons) by (the names of) their fathers, that is more just with Allaah. But if you know not their father’s (names, call them) your brothers in Faith and Mawaaleekum (your freed slaves)”
[al-Ahzaab 33:4,5]
It was narrated from Abu Dharr (may Allaah be pleased with him) that he heard the Prophet (peace and blessings of Allaah be upon him) say: “Any man who knowingly claims to belong to someone other than his father has committed an act of kufr. Anyone who claims to belong to a people when he has no lineage among them, let him take his place in Hell.” Narrated by al-Bukhaari (3317) and Muslim (61). 
See also question no.  5201 for an explanation on the difference between adoption and sponsoring an orphan. 
Thirdly: 
It is not permissible to name the orphan after your husband, because this is part of adoption which is haraam, and because that leads to negative consequences with regard to inheritance etc. Your desire to sponsor an orphan, which is a mustahabb action, does not make it permissible to do this haraam deed. 
Based on this, if you cannot sponsor the orphan except by adopting him, then you must be patient and wait for a way out from Allaah, may He be exalted, for His stores are full and everything is in His hand, and the one who keeps knocking at the door will soon have it opened to him. 
We ask Allaah to provide for you from His bounty. 
And Allaah knows best.