once you hatch an egg, the monster obtained becomes unobtainable for the rest of the run
if you get multiple eggs of the monster you want multiple of before hatching them, then you can have more than 1 of the same monster
ya basically this. Theres 2 ways:
1, The nest in the village makes a monster always appear in the team select at the start, but it can still appear randomly as well allowing you to be offered the same one twice at the same time.
2. The egg sense option at nests doesnt offer anyone whos already on your team but it doesnt look at your inventory. If you sense for a specific mon, but dont hatch the egg, you can sense for it again at another nest. Once you have as many as you want, then you hatch them all.