Sanatan Baishya warm welcome to this site as a new member and I can understand your position in the family. For a elder son like you the family responsibility is always more and the parents would expect more from you. Now having your sisters got married and also taking care of your parents , brother, it is now the turn for yourself to settle in the life. Normally the parents at the old age wants their son to be with them and he must cherish in life with children, But for few the work compulsion makes them to be away from the parents and that would be really taxing. I know by being away from the parents , you feel like left out and they also wont have the bonding required from you. What I suggest that if possible make transfer of your job near to your place so that the parents and brother are taken care off or leave the job and seek other job elsewhere.
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease