How can i get my baby brother back?

in 2008 my mom went to jail and she had my baby brother there and they told my dad that he needed to buy everything that a baby need so he did when it was time to go get my baby brother they told us that we could't get him bcuz my mom sing sum paper sayin she give the baby up.. my mom did't know wat was she singin she does't know english or read it.. wat can i do so i can get him back .. iam 20 and i go to college.. i went to different lawer they said no ... idk wat to do.. he is goin to 3 year old..