Caring for one's parents is a duty regardless of convenience.
Literal
Convenience [regardless-に関わらず] self's parents' care [object-を] do [topic-のは] duty is.
~に関わらず is a formal expression meaning 'regardless of,' connecting 便宜 (convenience/expediency) to the main clause. The のは...である frame topicalizes the nominalized action and equates it with 義務, creating an aphoristic tone. 自分の makes this a universal statement about everyone's obligation.