You are mixing up things. Pandu was cursed by a Rishi that he would die if he enjoy marital life with his wife as he had killed the Rishi's mate who were in disguise as "deer".
Of ocurse Dritarashtra was not eligible due to blindness, but his eldest Son would have been eligible.
Pandavas were not even sons of Pandu (due to above said curse). Atleast Kauravas were sons of Dritarashtra (albeit division of fetus by Veda Vyasa)!!!!!
