Waht are the chances more of my children will have tibial hemimelia?

It depends: There are two types of tibial hemimelia. The bilateral "syndrome" affects both legs and is believed to be autosomal dominant, so there would be a 50:50 chance that another child will be born with it. The unilateral tibial hemimelia (1 leg affected) is thought to be autosomal recessive and a 25% chance (1 in 4) of a child being born with it, and a 50% chance the child will be a carrier.