No. Every licensed operator allows one account per person, and duplicate accounts are grounds for confiscating bonus winnings and closing both. Sister brands on one licence usually count as the same operator.
The rule
One account per person, per household in some terms, at every licensed operator. It is in the terms you accept at signup, and it is enforced.
Why it exists
Bonus abuse mostly. A welcome offer is a marketing cost the operator accepts once per customer. It also serves anti-money-laundering duties: an operator has to know who its customers are, and one person behind three accounts defeats that.
How duplicates get caught
Name and date of birth matching, address matching, payment method fingerprinting, device and IP signals. Payment method is the one that catches people who thought they were careful, because the same card or e-wallet on two accounts is a direct link.
Sister brands count too
Many operators run several brands on one licence. Two sites with different names, different colours and the same terms of service are often the same operator, and their one-account rule usually spans all of them. The Terms of Service page names the licence holder, which is how you tell.
This is also why we deduplicate at operator level in our rankings: listing five brands from one company as five independent choices would be misleading.
If you already have a duplicate
Contact support and tell them before they find it. Voluntarily disclosing a duplicate account usually results in one being closed and any balance returned. Being caught after winning usually results in confiscated bonus winnings and both accounts closed.