Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh

 

Since you are a mature adult, you can decide for yourself whether you want to move out with the sister and give her company and help her out.

 

However, you cannot do so at the expense of the essential care and service you owe our father – if he cannot live without your assistance.

 

If, however, he is being looked after by his wife, you may decide to move out but do so with his blessing.

 

Almighty Allah knows best.