Complex sentence: Among the converts the Portuguese made, it cannot be denied that a large number of them were descendants of the Christian Community founded by Apostle St. Bartholomewand these new converts were not strangers to the old Christians.
Split into simpler sentences: Among the converts the Portuguese made, it cannot be denied that a large number of them were descendants of the Christian Community founded by Apostle St. Bartholomew. But these new converts were not strangers to the old Christians.