Short answer. The duty follows filiation, not recognition — so yes in principle. But without recognition nothing proves the filiation, and a father who denies it cannot be made to pay until it is established. In practice the case is about proof before it is ever about money.
What the law says
Illegitimate children shall use the surname and shall be under the parental authority of their mother, and shall be entitled to support in conformity with this Code.
RA 9255, Section 1 — Surname Of Illegitimate Children. Read the full provision →
What the law says
The legitime of each illegitimate child shall consist of one-half of the legitime of a legitimate child.
RA 9255, Section 1 — Surname Of Illegitimate Children. Read the full provision →
Support is not the reward for being acknowledged
Illegitimate children shall use the surname and shall be under the parental authority of their mother, and shall be entitled to support in conformity with this Code. The entitlement is stated as an attribute of the child, in the same breath as the mother's surname and authority, and before the provision says anything at all about recognition by the father. Recognition, when it comes, is the exception that opens the surname — it is not the condition on which support depends. A father does not create his obligation by admitting it, and he does not avoid it by staying silent.
Recognition is a shortcut through the proof
That said, an obligation nobody can prove is one nobody can enforce, and this is where the practical answer lives. The three modes of express recognition — the record of birth, an admission in a public document, a private handwritten instrument — are ways of putting filiation beyond argument in a single document. Where none exists, filiation has to be established in a judicial action before support can be pursued on it. The claim is not weaker in principle; it is simply front-loaded, and the evidence has to be assembled before the money is discussed.
What the case is actually about
Two questions get run together and should not be. The first is whether this man is the father, which is a matter of evidence — scientific testing, documents in his hand, communications, and the conduct of the parties over time. The second is how much, which is answered by the child's needs measured against the father's means, and only arises once the first is resolved. Anyone in this position should be gathering material on the first question. Records that seem trivial now are what the case is built from later.
The question resurfaces at the estate
A father who simply refuses to engage has deferred the issue rather than closed it, because filiation carries succession as well as support: The legitime of each illegitimate child shall consist of one-half of the legitime of a legitimate child. And the right to bring an action to prove non-filiation belongs to the father alone and only during his lifetime, so a man who genuinely believes the child is not his has a forum for that and a deadline on using it. Silence is not a strategy for either side.