The Mississippi River merges/splits with the Red River/Atchafalaya River at the Old River Control Structure.

The Orinoco River and Rio Negro are connected via a distributary, although this is the upper reaches of both rivers.

Deltas are commonly very large and involve several streams. The mouth of the Amazon River is more or less 100 miles distant. And the Brahamaputra and Ganges river delta involves 100s of channels that more or less crisscoss the entirety of Bangladesh.

Staten Island could be seen as between two ends of the Hudson.

Alexandria and Cairo are at the Nile delta.

Not in terms of the "guide" linked to. It looks at rivers as something creeping up from the ocean to higher lands. It's a perspective where a river travels upstream, even if it flows downstream, if that makes sense.

The author is saying two streams travelling up never split, only merge. I'm saying they do split [0]. An upstream split is a downstream merge.

[0] https://www.openstreetmap.org/#map=15/45.7293/4.8128