The Power of Family

The third most important "power" in (optimistic) works, right next to The Power of Love and The Power of Friendship.

While The Power of Love is about the healing and nurturing strength that comes from romantic love, and the Power of Friendship comes from the healing and nurturing strength that comes from the bonds of friendship, this trope is about the healing and nurturing strength that comes from family bonds.

Wether it's your "birth" family or a family who happily adopted you, you can be sure that the love shared between family members can indeed be a powerful thing. It can help pull off successful "I Know You're in There Somewhere" Fights, give fathers and mothers the courage to go Mama Bear and Papa Wolf, and give enough Heroic Willpower to overcome the harshest of obstacles and adversaries.

Since Evil Cannot Comprehend Good, you can expect villains to wonder why isn't the family at odds with each other like "real" families (especially if the villain himself/herself was the one trying to break the family apart).

No supervillain can defeat them as long as they are together.

Examples of The Power of Family include:

Anime

• Vegeta learning he has a son is what fully completes his Heel-Face Turn, as his love and admiration for Trunks is what inspires him to become a true hero.
•  Oh My Goddess displays this trope between Belldandy, Urd and Skuld, always ready to stand by each other and overcome any obstacle because of the love they have for each other. Also present between Keiichi and Megumi.

Comics

• In pretty much all versions of the story, Superman's love for his adoptive parents, Jonathan and Martha Kent, is what made him the All-Loving Hero  Hope Bringer that is better known as.
• The love the Teenage Mutant Ninja Turtles have for each other and for their adoptive father Splinter is what helps them overcome the dangerous obstacles they face.

Film

• In Frozen, Elsa's love for her sister Anna not only brings Anna Back From the Dead after Elsa accidentally freezes Anna, but it also gives Elsa better control over her ice powers.
• The Incredibles, which provides the trope image, is a perfect example of this trope. As much as the Parr bicker and argue, in the end they love each other deeply, and that love is what gives them the strength to overcome the sinister supervillains they fight.
• While this is the Central Theme of the DC Extended Universe, it's never seen more keenly than in Shazam. Billy's love for his foster family is what gets him to become less of a Jerkass and more of an All-Loving Hero, and in the climax all the Vazques siblings fight together against Doctor Sivana and the Seven Deadly Sins.

Western Animation

• All over the place in the 2017 DuckTales show. The love the McDuck family shares for each other is what keeps them going strong and overcome any obstacle.
• In My Little Pony: Friendship Is Magic, the Apple Family embodies this trope. The love they have for each other makes them able to overcome any obstacle. And since the Apple Family adopted Pinkie Pie as their own, the bond between Applejack and Pinkie Pie is this trope and The Power of Friendship at the same time.