[quote="JAGCath28, post:6, topic:217733"]
So, I guess my question overall is two-fold. 1) Were some jewish males in captivity forced to become eunichs? I'm looking for sources whether Biblical or secular historical.
2) And if they were, what were the implications once this happened? Were they prevented from being fully part of the Lord's community?
You've already addressed, in part, the answer to both of your questions. Take a look at Isaiah 56. I believe it is reasonable to infer that the eunuchs in question, those who appear to be lamenting their current state due to the fact that they are unable to produce offspring, are men who have men captured and mutilated. That answers part 1 of your question; however, for further evidence, the Torah and Nevi'im (Prophets) records sexual mutilation performed by Israelites on their enemies, but only after (or at) the enemies' death in battle. See for instance 1 Samuel 18:27:
"David went out with his men and killed two hundred Philistines; David brought their foreskins and they were counted out for the king, that he might become the king's son-in-law. Saul then gave him his daughter Michal in marriage."
Although the verse names only the foreskin, one might suppose that in the context of collecting their war trophies, David and his officers were not careful to take only the part specified. Circumcision is, of course, a precise and delicate surgery - collecting war trophies, not so much!
As for part 2 of your question, look at Isaiah 56, again. My ESV version offers the heading "Salvation for Foreigners" to this chapter. Participation in the future messianic salvation is offered to all who believe in the Lord and keep his commandments, regardless of origin or social condition. Since, as I've stated above, we can rightly intuit that the eunuchs mentioned in this chapter are captured men, possibly even Israelite men, it should seem evident that such men who were involuntarily mutilated were not excluded from the congregation.