Square owns the rights to Xenogears and Xenosaga was developed by Monolith Software, there isn't that much connection in the two games besides the name.
Well, there is a greater connection than that; Xenogears was "episode 5" in a timeline meant for 6 episodes. The Xenosaga games, while not sequels, were based on that same storyline but set earlier in the story.
So if I like bg I'll like dragon age origins
Maybe. Spiritual sequels can cause some contention among fans with the "similar but different" motif. It's not uncommon for the spiritual sequel to be considered more "cheap knockoff" than "continuation". Bioshock, for example, was very popular but many people who played it consider System Shock 2 the superior between them. While I don't regard Dragon Age as a cheap knockoff, I also don't consider it a spiritual sequel either; I've played both games many times and they just don't feel similar to me. So to me, in this sense I see the "spiritual sequel" title more of an empty claim to try and grab up a demographic notoriously bitter about modern games.