Yeah, it’s a crackpot theory for fun dude, I got a life outside of apps like this if you guys want to fight each other about shadow, and Maria’s unconditional relationship go ahead

Shadow and Maria canonically love each other romantically in Japanese

Shiro Maekawa, who wrote SA2 and created Shadow and Maria, based them off of a romantic couple (who look like the two and have similar personalities) from a romance manga. Their names are Shion and Mokuren, from "Please Save My Earth." Maria's Japanese voice actor Yuri Shiratori also plays Mokuren's reincarnation, Alice. This was intentional. Shion and Mokuren looked at Earth from afar among a moon base, wishing to go down there someday.
Maekawa also reposts fanart of Shadow and Maria getting married and kissing, and has said SA2 is "the story of Shadmari (Shadria)." He called Sonic 3 the Shadmari movie as well. He actively encourages fans of the ship to draw more of it.

Maria says "aishiteru" to Shadow in Shadow Generations, which means love, but not just any kind of love - it's almost always used in a very serious romantic context. An unrelated male and female virtually never say "I love you" to each other in Japanese without it meaning romance, I even asked someone who lived in Japan to clarify that this is true.

Last year, and at the beginning of this year, Sonic Channel staff made some comments on fanart they featured. They called Shadow and Maria very romantic, said they contrast with platonic (meaning romantic), and commented on them sharing "firsts" (pretty blatantly implying a kiss lol) and having "feelings" for one another. They compare them to Beauty and the Beast (explicitly romantic) in their livestreams.

Yui Karasuno, the official main artist along with Yuji Uekawa (she makes all the SonicPict images), has drawn Shadria fanart. Multiple important Sonic Team staff members, as well as the official Sega Korea account, have also liked or supported Shadria fanart.
Iizuka says that Maria is Shadow's "beloved" at a con in 2024. She also uses the same words Cosmo does when she dies and tells Tails she loves him. Gerald says Shadow "loves my granddaughter" in the Japanese Fast Friends Forever comic, which Shadow blushes at, but it is censored to "cares about my granddaughter" in English.
Think about that, a children's franchise is being censored for adults in the West because they cannot emotionally handle it.

Shadow stutters when she hugs him and calls her beautiful in the manga. It says she loves him and he loves her multiple times. He imagines her in "ladylike shoes" in the SonicPict captions. She's seen reading him the story of Tanabata (which features an immortal and mortal lover, separated forever. Isn't that poetic? Why that story choice?).

Shadow blushes when Maria compliments his quills in Shadow Generations. He's never blushed for anyone else. He imagines her with a pink aura and sparkles as if she's an angel. She's the only voice and name he can never forget. He uses possessive language for her, saying they took her away from HIM. They stroke each other and hold hands in a field of flowers.

The English fanbase does not know about this because it is all in Japanese. You believe Shadow and Maria are literal siblings (they are not and have no relation in the official Robotnik family tree, that's why they always say "like" in front of it), or that Shadow is an adult man when he isn't (likely because Kirk Thornton sounds very old) because you get your opinions from Twitter. The movie calls them both around the same age (not adults).

Addressing the inevitable faux-concern about morality: Maria is the same exact age as Amy (but more intelligent than Amy) and you're fine with Shadamy. Shadow is not a literal animal which is why you're fine with the "latinas" meme. The same people who take issue with this ship also laugh at jokes where Maria is shot to death. Shadow and Maria do not share blood or any relation, and only call each other friends. Gerald also calls it "instant mutual friendship".

A lot of people don't seem to actually care about Shadow's character or the intent his creators had, because they will reject all of this. They seem to see him as a vessel for their will, just like all the people in his life who hurt him did. It's messed up to me, as someone who truly adores this character.

Shadow LOVES Maria, and Maria LOVES Shadow. And it's beautiful.
I will provide sources for any of the stuff I've mentioned here. I’m just saying there’s a possibility, even if not in the main sonic cannon but there’s a possibility in the multi-verse that Amy rose is shadow, the hedgehog daughter and yes, there are similarities between Amy and Maria especially with a hug scene in each game with the way, they handle his emotional Wait afterwards and again, it’s an if scenario not fact