Your counter examples actually reinforce the marriage metaphor. Remember, magi have many examples of marriage from history and myth to draw upon.
but still, I am fully aware the whole introduction part is just fluff. I like to write things as whole and complete. Still, skip all of that and just read the meaty part in the second half.
If ye fear that ye shall not be able to deal justly with the orphans, Marry women of your choice, Two or three or four; but if ye fear that ye shall not be able to deal justly (with them), then only one, or (a captive) that your right hands possess, that will be more suitable, to prevent you from doing injustice.
—Qur'an, Sura 4 (An-Nisa), Ayah 3
I can imagine a familiar that is a group of creatures, like a wolf pack. Or my own herd of cats. Or what if a single Familiar had multiple magi? Like, say, maybe a Daimon?
If you think of binding a group of creatures, think about a swarm !
It would be a nice concept to have a magus with a bee swarm as familiar or an ants colony.
In a old campaign (2nd ed !), my magus was a Beast master who developped a 4th type of cord, the Heart Cord (after the gold, silver and bronze one). It allowed him to bind a number of familiar equal to the Heart Cord value. He used it to bind a couple of faerie dragons. It was mostly a "cool look" thingy since benefits were limited - yes you could send the familiars in different places and be able to see through their sense, but otherwise, there was no other tangible benefits, there was no stacking of boni. It was one of the things he developped to claim his Archmagus title.
I had a player in my last Saga take a King of Bees as a famlier. (Mythic Bees are ruled by a King not a Queen) While the Magi wasn't "bound" to the swarm I Generally assumed the King's subjects came with the package.
(My maga, Deborah, in an abortive online saga here in which we both had played, had a very powerful Spirit of Creepy Crawly Creatures as her familiar, and was the center of massive swarms of creatures. My Ars Magica version of a Shadowrun Insect Shaman /2. I don't think either Deborah or the spirit thought of their relationship as marriage, FWIW...)
Oh, yeah. One Tytalus has a pig familiar, another has a dog, and the third is a Bjornaer with a Boar Heartbeast, and they start a covenant in the Levant. The Bjornaer doesn't understand why the locals so revile them, or why the Tytali are grinning so much.