Enos

Enos 1:11 And after I, Enos, had heard these words, my faith began to be unshaken in the Lord; and I prayed unto him with many long strugglings for my brethren, the Lamanites.
12 And it came to pass that after I had prayed and labored with all diligence, the Lord said unto me: I will grant unto thee according to thy desires, because of thy faith. When Enos prayed for the Nephites, the Lord said, "I'll bless them if they're good and punish them if they're bad," or "naw, not going to change what I was planning to do with the Nephites just because you prayed about it." But when he prays for the Lamanites, the Lord says, "ok. I'll do what you're asking."
Of course, you've to remember that the Nephites and Lamanites mingle and blend around the coming of Christ so there isn't necessarily any specific genealogical tieback to Laman himself when they finally kill all the Nephites.