Final answer:
Using logical deduction, R is related to P as his sister, as they both share a common family link via J's only son-in-law, Q.
Step-by-step explanation:
The relationship puzzle to determine how R is related to P involves interpreting complex family ties, using concepts of kinship, lineal relationships, and marriage customs. Despite the various cultural implications and practices such as the levirate and sororate rules, this question seems to rely purely on logical deduction rather than specific cultural norms.
Since R is the sister-in-law of L, and A has only three children, it can be inferred that R is likely married to one of L's siblings, thus making R the spouse’s sister. Not considering marriage customs, we can deduce that R is P's sister, if Q is J's only son-in-law and P is the only brother of Q.