Short answer
A large age difference is not automatically a reason for rejecting a marriage, but practical compatibility should be considered carefully.
Islamic Guidance
What Islam teaches
Islam does not establish one universal age difference that makes a marriage valid or invalid. Suitability and mutual rights remain important.
Practical Guidance
What you can consider
Consider maturity, health, future plans, children, lifestyle and expectations rather than focusing only on the number of years between spouses.
Sources
Qur'an 30:21; Qur'an 49:13.