My bother cant see his newborn son?

Je
Opinions please. So what do yaw think about a mother giving her son her mothers maiden name rather than the biological present fathers last name? My brothers fiance just had their baby a few days ago. Her mother told her to give the baby her last name rather than the fathers. Note they are both 19years old. I am 23 and 15weeks. I can see how much pain my bother feels like his little family is broken and now all of a sudden his fiance dont want him now. Her mother also told her not to let any of the fathers family get to see the baby. While at the hospital her mother wouldnt let the other grandparents or uncle or the father come. Now i have been trying to keep my cool and i was able to talk the mother into letting my brother to stay to see the birth of his son but now that their home ( which they both live with their parents) non of the fathers family including myself and the father, have got to or are allowed to see the baby according to the mother of the mother. This has been very heart breaking for all of us and not sure what to do? Its hard for me to be excited about my pregnancy while seeing my brother hurt so bad. Far as I know he hasnt done anything for them to be so cold.