Are you thinking of a triplet then? That definitely focuses your options. I don't know anything about triplets, but I would think that anyone that does and would like to help you will need to know: age of the child, yours and DW's dimensions, and of course what kind of riding will be expected. I don't believe triplets are terribly common. Almost certain they are all semi to fully custom and there is probably not a lot of variation in an overall high quality product paradigm between competitor manufacturers.