Complex sentence: He was repentant, asking God to bless the king, queen, and their "royal progeny", but "spoil (ed) all the pottage with one filthy weed" by beseeching God to make the king a Catholic.
Split into simpler sentences: He was repentant, asking God to bless the king, queen, and their "royal progeny". He did, however, "spoil all the pottage with one filthy weed" by beseeching God to make the king a Catholic.