My cousin Siraj startled me the other day. He emailed me from his home in Washington DC, urging me to open my heart and accept Islam. I know you have been contemplating the step of becoming a Muslim for some time, he wrote: do it now, in the holy month of Ramadan!

Becoming a Muslim, I thought … What the heck did he think I had been all these years, from birth onwards? My father was certainly under the impression that he had fathered Muslim children: saw that the azaan was said over us at birth, took his son (though obviously not his daughter) with him to Friday prayers at the local mosque. And anyone who understands Muslim names would know straightaway from mine that I am part of that family. "Do you practise?" they might well ask, and I would say that I didn't, and that would be alright.

So what, I fumed in the Delhi heat, was my cousin Siraj on about? What makes a Muslim, I wrote back with deceptive rationality and meekness. If it is the personal revelation, I argued, then there are hundreds of people around the world who consider themselves as Muslims but are nothing of the sort.

But once I had calmed down, I began to see interesting issues emerge around nationality, ethnicity and faith, ones that Siraj bhai had usefully stirred. I consider that I have a Muslim identity because of familial loyalties and ethnic ties. I have inherited my Islam in much the same way as many in the UK will automatically write "C of E" on their hospital admission forms. There is – so far as I know – no ceremony at puberty similar to confirmation or bar or bat mitzvah when an individual proactively takes on the faith into which they were born as an individual. But even if a Jewish child does not have a bar or bat mitzvah, he or she does not of course cease to be Jewish.

Despite the azaan I myself grew up in pretty much of a spiritual vacuum: a kind of Bermuda triangle of faith – marooned between a father whose religion was real but private and a mother whose German socialist roots made her uneasy about religion (and about being renamed Mumtaz Begum). And as double immigrants, they were anyhow too focussed on finding a foothold in an alien society to put religion high on their agenda.

But I missed it. I was the sort of child that seems to have been born with a faith gene. And I remember moments in childhood that had convinced me then not so much of a God as a transcendent reality (if you can put that in an 8-year-old's terms). So when we were on holiday in the year when I was 11 and I ran across a children's seaside mission on the beach, it was a revelation. More, the pastor was one of those rare individuals who understood that children can care about spirituality, and could communicate with them, vividly and with deep respect. It was a seminal moment for me and – to the fury of my father who forbade me to do anything of the sort – I announced I had converted.

Ultimately, Christianity did not take. It was quickly killed off by glum Sunday rites at boarding school. In my own time, I beat my own way to the satisfying rigours of Zen Buddhism. But paradoxically, the more I explore, the greater my appreciation of spirituality in general, the greater my respect for my root religion, and the greater the urge to read, understand and acknowledge – keeping for instance, the Ramadan fast – the thread that binds me to Islam.

Politics has also had much to do with it. The pillorying of Islam and the wilful misrepresentation of it as a bloodthirsty, barbaric religion cannot have failed to have an impact, and make those of us with a different perspective not wish to give any apparent comfort to its detractors. In a number of cases it has pushed people into allegiances that are not wholly religious. It has been a crude shoe-horning. Islam is no more confined to people of Middle Eastern/Asian origin than Christianity is to westerners. (American Muslims have roots apparently in over 80 countries.) But the definition has been thrust upon us, and hard not to take it as a challenge. I started wearing a taveez when the Ayodhya mosque in India was demolished by Hindu fundamentalists. It is a gesture maybe of no more than respect, but I see no reason to remove it.

My Islam is part of my identity. It is part of my loyalty – or faithfulness – to my roots and the reason why both my children have Muslim middle names. It honours my family members whose practice is thoroughgoing and profound. Zen, meanwhile, points to the "emptiness" or limitations of categories and their essentially conditioned nature. To talk in terms of exclusivity makes no sense to me, but a balance of faith and faithfulness does.