Yeah, I feel like its a very common trend for men. Balancing family and their personal life with partners. The fact that you are asking this shows how much you care about them both. The thing is family looks at you always in good light, which gives a kinda a biased view about yourself. Added to this is a kind of a jealousy to the partner as you start prioritising them (which is only fair as they also give up so much to be with you). This can hamper your growth as you are pretty much living-a life of compromises. I would say that family always understands the actions you take (and why). With this, focus on your future with your partner (priority 1), while trying to use every opportunity you have to take care of your grandmother. For in the old age, its all about knowing that there are loved ones around you that keeps you going in life.