Family businesses are often as much a venture of love as of money. Over time that can lead to situations where family members are undervalued with no annual pay rises, or additional recognition, and even no formal contract.
You can head off problems at the pass and work through any simmering resentments that this may have caused with a neutral party. Equitable relationships in work lead to better home relationships too.
Action step: Why not take some time out to identify someone to work with on this issue?