À présent qu'il est vieux, c'est ton devoir de veiller sur lui.

[corgwin24]

English Translation

Now that he is old, it is your duty to go look after him.

veiller sur

1. [surveiller - enfant] to watch (over), to look after, to take care of
2. [- santé] to watch, to take care of
   © Larousse 2014