SMAASH! Puppy
Smash Legend
They technically ARE different series.
You can't make ties or continuations to a game series you don't own own. This is why we got Dark Souls and not Demon Souls 2.
So literally, no, but if they were no one would bat an eye. Got it.They are different series as they are different IPs owned by different companies.
However some people (like me) prefer to think of them as a pseudo series as they were created by the same people and have lots of elements in common (about as many as any two given mainline FF titles or more, to use an example).
Not everyone likes this view though and these conversations usually turn ugly so that's all I have to say about it.
What about Xenogears and Xenosaga though? Are they of similar relation?