I joke that it takes 19-22 extra organs just to make up for having a stunty half-size chromosome ;). Especially when I win.
I definitely see SoB as a marine-like army, though were at the far edge of that. As I said, we're "marineier" than GK or Deathwatch, which are actually marines.
The Codex: Space Marines, Space Wolves, Dark Angels, and Blood Angels are "Space Marine armies". They all basically share the same unit pool and core functionality and capability, with a few special units and upgrades each. Grey Hunters, Tacticals, all the same basically.
Grey Knights and Deathwatch are technically ADEPTUS ASTARTES, but aren't "Space Marine armies", because their units are completely different and function is completely different. GK have terminator troops and Strikes all have force weapons, and no heavy weapons are shared in common. Likewise, a Deathwatch Kill Team is also nothing like a Tactical Squad, it's got special weapons for everybody, all kinds of loadouts, mixed unit types, etc. In addition, their playstyles are completely different from the Space Marine codecies. BA being "different" from Codex Marines is basically just a matter of leaning on their special units. In playstyle, you can have functionally identical Space Wolves, Blood Angels, Dark Angels, and Codex: Marines armies. I play SW as a bunch of Long Fangs and Grey Hunters and Primaris troops, and could easily just say "well, I'm Iron Hands today" and change nothing about my army. Grey Knights, on the other hand, are all on the drop, extreme low model count, and universally heavy-medium melee and play very differently. Similar for Deathwatch.
I consider Sisters of Battle to actually be sharing space with GK and Deathwatch both lore wise and mechanically as "Inquisition Armies" or "Marines but not Marines". We're the closest to Space Marines out of the three in terms of rules [sharing unit types, functions, and loadouts], but we're also just different enough to have our own identity on the tabletop [mostly due to lack of 48"+range more than being T3. The T3 isn't really significant]. Primaris Marines have really made that distinction more defined.
I've run Deathwatch a couple of times, and I've got Space Marines in my W&G party, and I've got a Space Wolves army. [I've also got a IG, SoB, GK, and Talons army] I don't really have a problem with them.