This story is a sequel to Don't Forget To Remember Me

Shining Armor leads a wonderful life with his wife Cadence and daughter Flurry Heart. But he doesn't get back home to Canterlot much. So when his mother calls him home to visit, he's eager to go. Until he learns the reason why she called him. Everything he's known about his family is shattered in an instant. Luckily, his mother is there to comfort him.

Slight regression, but not too much. It's reasonable.

Check out the prequel and companion piece Don't Forget To Remember Me.