Although the circumstances are unusual, if a person is not the biological parent and is neither married nor the adoptive parent, they really don't have standing to sue for custody/vistation in Michigan.

The case is really no different than a boyfriend trying to obtain custody/visitation to the children of an ex-girlfriend with whom he used to live.
Custody battle


"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungleā€”as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.