Shining doesn't feel very keen on having a foal or filly to look after.
He'd much rather have a niece or a nephew.
So, with Twilight being his only sibling,
and the only pony she seems to have a thing for is Flash,
(at least, that's what Shining thinks.)
The captain puts two and two together and comes up with one simple solution.
"PRIVATE! I order you to buck my sister!"
~And to this day, Atlas still regrets ever writing this fan fic~
Shining wants to be an uncle, and Flash DOES NOT want to be a father, too bad for him, since Shining will make sure it will happen one way or another.
(A sequel to "I want to be an uncle") Flash decides to tell Cadance about Shining's plan of wanting to be an uncle in hopes that she'll understand how asinine it is, and she does understand, but not in the way Flash would think.
(A threequel to "I want to be an uncle.) Knowing that there is now way out of this, Flash travels to Twilight's house and prepares for the worst, only to find out that she has the same intentions as the rest of her family.