The fire-sign parent and fire-sign child
This is often quite a felicitous combination, with much laughter, excitement, shared fun, and adventures. When the child is grown, the pair are likely to be excellent friends.
The fire-sign parent is often highly ambitious for their child's success, and this can inspire the fire-sign child's own drive to excel and "be the best" in some way. However, bringing two fiery people together, especially when one is more dominant or "over" the other one, is likely to produce sparks sometimes!