Ageless Entity

Whenever you gain life, put that many +1/+1 counters on this creature.

Aragorn and Arwen, Wed

Vigilance
Whenever Aragorn and Arwen enters or attacks, put a +1/+1 counter on each other creature you control. You gain 1 life for each other creature you control.

Sunbond

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Lathiel, the Bounteous Dawn

Lifelink
At the beginning of each end step, if you gained life this turn, distribute up to that many +1/+1 counters among any number of other target creatures.