Yes, Jains can eat pumpkin.

• Pumpkin (kaddu) grows above the ground, on a creeper.
• Jain food rules mainly forbid root / underground vegetables (potato, onion, garlic, carrot, beet, radish, etc.) because uprooting them causes more himsa (violence).
• Pumpkin is not a root, so it is generally allowed for both Śvetāmbara and Digambar Jains in normal days.
• Even in many Paryushan / Chaturmas lists, pumpkin is mentioned as an allowed vegetable.

If someone in your family avoids pumpkin, that is usually a family or local tradition, not a general Jain-dharmic restriction.

You can read more here

• Why pumpkin is allowed in Jainism
• List of allowed vegetables (including pumpkin)