Is it better not to mention that I have relatives in the UK during visa application to avoid migration suspicion?

No, hiding your UK relatives is one of the riskiest moves you can make on your application. UK Visas and Immigration cross-checks applications against shared databases, and if your omission is caught, you face an automatic refusal and a possible 10 year ban from entering the UK. The safer route is disclosing your relatives openly and building a case around your intent to return home.

What Happens If You Hide Versus Disclose

How to Disclose Relatives Without Raising Suspicion

• Submit a clear cover letter stating you have family in the UK but your primary purpose is a temporary visit or study, and that you will return home afterward.
• If staying with relatives, include a signed invitation letter plus their UK passport or residence permit; if not, book independent accommodation to show you are not relying on their network.
• Provide employment letters, payslips, property documents or tax returns from home to prove your ties there outweigh your ties to the UK.
• If you have dependents like a spouse, children or elderly parents at home, mention them, since this strengthens your case to return.

My Advice

Write out your relationship to your UK relative honestly on the form, then spend most of your effort building the home ties section of your application, since that is what actually decides your outcome. If you are a student, add a letter from your school confirming your enrolment and expected return date to reinforce your intent.