The layout suggests to me a Presbyterian baptism register. Killylea is in the parish of Tynan. There are 3 Presbyterian churches in that area. Middletown has baptisms from 1829 onwards, Lislooney from 1836 and Drumhillery from 1829. So the entries may be from one of those. There are copies of the first two sets of records in PRONI in Belfast. For Drumhillery, the Minister has the only copy.
The townland for the second baptism looks like Tirearly (parish of Lisnadill).
It wasn’t unusual for 2 brothers to marry 2 sisters. I have come across that before.
I agree the second baptism appears to be for Sally and mother’s maiden name was Kilpatrick. Sally & Sarah are interchangeable so you might find that lady in later life calling herself Sarah. Kilpatrick and Kirkpatrick are likewise interchnageable and folk often swapped between the two.