Saroj is the mother-in-law of Vani, who is the sister-in-law of Deepak.…

Concept: In blood-relation puzzles, translate every marriage-based term (sister-in-law, mother-in-law, brother-in-law) into a direct family link, then connect the generations through any parent the clues actually name. A well-posed puzzle has exactly one reading of its terms that produces a fully determined answer; use only the people the clues introduce, and take stated relations like "brother" at face value (full siblings sharing both parents) unless told otherwise — any other reading leaves some link unresolved.

Applying it here:

1. Deepak has exactly one brother, Ramesh (given directly), and no other sibling or spouse of Deepak's own is mentioned anywhere in the clues.

2. Rajeesh is stated to be Ramesh's father. Taking "brother" at face value (full siblings, same parents), Rajeesh is Deepak's father too.

3. Vani is Deepak's sister-in-law. Reading this as "wife's sister" would need Deepak to have a wife, which is never stated — that leaves Vani's own husband, and so Saroj's identity, completely undetermined. The only reading that ties Vani to a definite person is that she is married to Deepak's one named brother, Ramesh, making her his wife.

4. Saroj is Vani's mother-in-law, meaning Saroj is the mother of Vani's husband, Ramesh.

5. Since Ramesh and Deepak share the same parents, Ramesh's mother, Saroj, is also Deepak's mother.

Cross-check: Rebuild the family tree from the result: Rajeesh and Saroj are the parents of both Ramesh and Deepak; Ramesh married Vani. Every clue, Vani is Deepak's sister-in-law, Saroj is Vani's mother-in-law, Rajeesh is Ramesh's father, Ramesh is Deepak's only brother, is satisfied by this tree, and it is the only reading that leaves nothing about Saroj's identity unresolved.

Answer: Saroj is Deepak's Mother.