There is no legal impediment to hold you back from exchanging greetings through shaking hands as a sign of warm greetings and heartfelt welcome as long as there is no risk of intimacy or fear of rising lusts. It was reported through al-Bukhari that Anas ibn Malik narrated that, “girls from al Medinah would take the Prophet’s hand and wander with him where they want”. As for shaking hands with women, Imam Ahmad reported that it is a disliked act. The majority of scholars except for the Shafi’is do not permit shaking hands between male and female youth. The Shafi’is permitted shaking hands between the youth of the two sexes with two conditions: no risk of intimacy and existence of a barrier.
Therefore, if reasons for mixing between males and females exist along with safety from any potential lusts then it is permissible to shake hands when necessary such as greetings after travelling or greetings during visits etc…
God has forbidden us from committing sins and entertaining immoralities or even approaching them, God says, “…And do not approach immoralities - what is apparent of them and what is concealed...” (Quran 6:151). Part of approaching immoralities and sins is committing what would lead to them; there is no doubt that hugging between males and females (who are eligible legally in Islamic law to marry each other) can very well be considered as an introduction to sin that may follow suit.
Therefore hugging and kissing between males and females whether relatives or not (as long as they are legally eligible to marry each other) is absolutely prohibited as hugging and kissing raises possibilities of intimacy and runs the risk of lusts. What you need to do is to kindly inform your male relatives that you will not be able to hug and kiss them for religious reasons with the hope that they respect your personal choice and religious beliefs.