All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
If the heirs are only those mentioned in the question and the deceased did not leave any other heir, then the husband gets half of her estate as his legal share due to the absence of direct heirs (children); Allaah says (what means): {And for you is half of what your wives leave if they have no child. }[Quran 4:12]
The other half is given to the full-brother by ta’seeb (by virtue of having a paternal relation with the deceased and not having an allotted share, so he gets what is left after the allotted shares have been distributed).
As regards the people whom you mentioned in your additional information, they have no share in the inheritance.
Also, it should be noted that adoption is forbidden in Islam, and it is not one of the causes that give someone the right to inherit. For more benefit in this regard, please refer to fatwa 119119.
Allaah knows best.