Am I allowed to sell my shares for less than they're worth to keep it in the family?

Yes, you're generally free to sell your own shares for whatever price you choose, including well below fair market value — Ontario corporate law doesn't set a minimum price for a private share sale between family members. The catch is on the tax side: Canada's tax rules can treat transactions between related parties differently, and selling below fair value to a related person can trigger tax consequences based on the fair value of the shares rather than the lower price actually paid, meaning the seller could face a tax bill calculated as if more had changed hands.

There can also be family-fairness consequences if other children or beneficiaries later feel the below-value sale effectively favoured one sibling. Before finalizing a below-market family sale, get proper tax advice on how the transfer will actually be treated, and document the reasoning — with independent legal advice for each side — so the transaction holds up if it's ever questioned later, whether by tax authorities or by family members who weren't part of the deal.