Is the word filho the same in Brazilian and European Portuguese?

No

While the spelling, grammar, and core meaning (referring to a male offspring) of the word "filho" are identical in both varieties, there are notable differences in pronunciation and typical usage:

• Pronunciation: In Brazilian Portuguese, the vowels are generally more "open" and the rhythm is more melodic. In Continental Portuguese, the vowels are much more "closed" or reduced; for example, the final "o" in "filho" is often very short or nearly unpronounced.
• Typical Usage: In Brazil, "filho" is frequently used as a term of endearment or a vocative (a way to address someone) for younger people, even if there is no biological relationship. In Portugal, the use of "filho" as a vocative is much rarer and usually strictly reserved for actual parental or paternalistic contexts; a Portuguese person would more likely use "miúdo" (kid) to address a child.
• Accompanying Grammar: While not a change to the word "filho" itself, the way it is used in a sentence differs. Portuguese speakers almost always use a definite article before possessive pronouns (e.g., "o meu filho"), whereas Brazilians often omit it ("meu filho").

Brazilian Portuguese Examples

1. Meu filho está dormindo. (My son is sleeping.)
2. Oi, filho, tudo bem? (Hi, kid, is everything okay?)
3. Eu amo meu filho. (I love my son.)
4. O meu filho é muito esperto. (My son is very smart.)
5. Onde está o seu filho? (Where is your son?)

Continental Portuguese Examples

1. O meu filho está a dormir. (My son is sleeping.)
2. Olá, miúdo, tudo bem? (Hi, kid, is everything okay?)
3. Eu amo o meu filho. (I love my son.)
4. O meu filho é muito esperto. (My son is very smart.)
5. Onde está o teu filho? (Where is your son?)