Ekuar was captured by the Trolls when he and his two companions were children. I assume they were guarded around the clock. If so, I guess that Mekda was never allowed enough contact with either of the boys to conceive a child. (Not sure why Guttlekraw didn't think to use them as breeding stock for more Rockshapers - his cruelty knew no bounds.)
By the time Rayek freed him, Ekuar was older than Savah. The two of them lived with the Go-Backs for a few years, and were intimate with them. The Go-backs aren't much into nuclear family structure. So I wonder if Ekuar is capable of fathering children, and if any of the Go-Backs are his offspring.