Explanation:

Let’s break this down step by step:

- We've got 7 family members, 3 generations, birth years: 1961, 1966, 1973, 1986, 1995, 1996, and 2002. Ages (in 2020): 59, 54, 47, 34, 25, 24, and 18.

- B is the wife of the oldest (born 1961, aged 59).

- 1966 (54 yrs) is grandma to C (so this is a woman, married to 1961-birth guy).

- B has only one child, who is married to E's daughter. E has two kids.

- D is the only brother-in-law to E's son. That means, E’s son’s wife has one brother: D.

- F is older than G but younger than D.

- Brother-in-law of D born in a leap year. Leap years given: 1966, 1973, 1996, 2000, 2004, but here 1966 or 1996 seems likely from other clues.

- Person born in 1986 (34) has only one child.

- 1966's person is also mother-in-law to 1995-born. So 1995 (25 yrs) must be married to 1966’s child.

- Child of F is born in 21st century: so that's 2002 (18 years old child, F's kid).

- Father of the person born in a year which is a multiple of 5 (1995) has a prime-numbered age.

Let's connect these:

- 1961 (male), 1966 (female): oldest couple.

- B = wife (1966), A = husband (1961).

- A & B have only one child, who is married to E’s daughter.

- E has two kids, one is E's daughter (married to A & B's child), one is E’s son (who has brother-in-law D).

- F has child 2002, so F must be 1973 or 1986.

- Person born 1986 has only 1 child: must be F.

- So F = 1986 (34), child G = 2002 (18).

Ages breakdown:

- 1961: 59

- 1966: 54

- 1973: 47

- 1986: 34

- 1995: 25

- 1996: 24

- 2002: 18

Who is father-in-law of only son of A (1961)?

A & B's only child is married to E's daughter.

So E is father-in-law to A&B’s only son (C). Father-in-law to C = E.

C must be E’s daughter’s husband, so C = A & B's only child, married to E’s daughter.

C could be:

- Born 1995 (married), so C = 1995 (25). E’s daughter = C’s wife.

Now, who is the father-in-law of only son of A?

That means: Who is E?

E must be generation 1966 or 1973 (older generation, since his daughter is married).

If E is 1973 (47), perfect fit—a parent to someone born 1995.

Check: The age of father-in-law of only son of A is 47 years.

So, the correct answer is Option 2: 47 years.

Summary of clues:

- Grandparents: A (1961, 59), B (1966, 54)

- Their child C (1995, 25) married to E’s daughter.

- E = 1973 (47), two kids: daughter (married to C) and son.

- F = 1986 (34), G = 2002 (18, F's kid), one child.

- All statements align.

Option 2 is the one you want. 47 years is the answer.