Parents:
Mothers: Twilight Sparkle, Sunset Shimmer, & Tempest Shadow (AKA Fizzlepop Berrytwist)
Father: Flash Sentry
Children by Parent (From left to right):
[Twilight & Sunset]:
Sunshine
[Twilight & Flash]:
Starburst,
Night Light Jr.
[Twilight & Tempest]:
Nightfall
From Oldest to Youngest:
Starburst & Sunshine (Born around the same time)
Nightfall
Night Light Jr.
Story:
Sometime after the great battle against the Storm King, Tempest opted to stay in Ponyville, even becoming a member of Twilight’s personal Royal Guard as a way for atoning for her actions, eventually becoming second in-command, out-ranked by Flash himself. Later after her graduation, Sunset decided to finally return to Equestria, with Twilight and her lover Flash allowing her to live in the castle where she began work as Twilight’s assistant.
Over time the four bonded over studying magic with Twilight, sharing stories with the couple about events and adventures they’d had, and even having several sparring sessions (with Sunset discovering she had a knack for combat magic). As time went on both Tempest and Sunset grew closer to the loving couple, to the point where their friendship turned into romance, which soon escalated into “special sessions” between them behind closed doors…
Eventually, with a bit of “all-night convincing” for Flash and Tempest (as well as Twilight going through several law books before successfully legalizing polygamous marriage), she and Flash agreed to an open relationship and welcomed Sunset & Tempest into their family, and a few years later Starburst & Sunshine were born.
Tempest needed the most time to adjust to this new lifestyle, but soon softened up as she slowly bonded with the children, she eventually mellowed out after giving birth to Nightfall, and even more so when Night Light came into their lives…
(For those of you wondering about Sunray, in this version Human Flash got together with Human Sunset.)