A son from a different relationship?

Does anyone have a son from a different relationship or does your partner? 
​If so do you get on with your partners child, could you raise him or her as your own? 
​I have a friend who has been asking me these questions . She loves her husbands son and he's grew up knowing and calling her mom so would and should she say "trying to conceive  baby no 2- Ttcor 1 . Considering the 1st baby isn't hers  does saying ttc 2 sound weird?