This puzzle seems designed to obfuscate and frustrate at every turn. Having said I was going to leave it, reluctance to admit defeat made me pick it up again. Applying some logic I was able to deduce the precise arrangement of the shape. I will give credit to the setter for engineering the grid so that this is possible. Even then nothing jumped out until I noticed one sequence of letters that, if completed, would render a name with which I was familiar; I then saw two others of the same family. Since the names are unusual I don't see how anyone unfamiliar with them has much hope.
I thought then I was home and dry, but oh no! I cannot see anything that I recognize from the other collection of letters, which appear to have nothing whatsoever to do with the first set. I shall persevere, desperately entering various combinations into Google.
I think that in puzzles with elements hidden in the grid, the setter should give the solver some steer towards what to look for, but here there seems to be nothing. Even "three members of two families" isn't much help, given the title. They could vegetables and fruit.
Incidentally, on an unrelated matter, two clues are presented as & lits, but I don't quite see how a clue in which the wordplay generates an extra letter can be & lit.