Hi Aspirant,

No it won't affect even if there is a 2 year  gap between 10th and 12th.To be eligible for JEE Mains and Advance what matters is your 12th qualification.

JEE Main Eligibility Criteria:

• Any candidate who has passed class 12th or its equivalent in the year 2019, 2020, or appearing in 2021 can apply for JEE Main.
• There is no age limit.
• Students can participate in the JEE Main for 3 consecutive years.
• Should have passed 10+2 with Physics, Mathematics as compulsory subjects and any one of (Chemistry, Biology, Biotechnology, Technical Vocational Subject).

You can refer to below link for further information regarding eligibility criteria for JEE Mains,

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

JEE Advance Eligibility Criteria:

• Only JEE Main qualified candidates will be eligible for JEE Advanced 2021
• For JEE Advanced 2021, the candidates should have been born on or after October 1, 1996. But,SC, ST and PwD candidates will get a relaxation of 5 years (born on or after October 1, 1991).
• The maximum number of attempts that the candidates can attempt JEE Advanced is two times in two consecutive years.

You can refer to below link for further information regarding JEE Advance Eligibility,

https://engineering.careers360.com/articles/jee-advanced-eligibility-criteria

Good Luck!!!