彼は、せいぜい２、３歳僕より若いだけです。

He is not more than two or three years younger than I am.

彼(かれ)は、せいぜい２、３歳(さい)僕(ぼく)より若(わか)いだけです。

Kare wa, seizei ni, san sai boku yori wakai dake desu.

彼 (かれ)

he; him; his; boyfriend

は (は)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

精々 (せいぜい)

at the most; at best; to the utmost; as much (far) as possible

二 (に、ふた、ふ、ふう)

two

三 (さん、み)

three; tri-

歳 (さい)

-years-old; ability; gift; talent; aptitude; genius

僕 (ぼく)

I; me; you; manservant

より (より)

than; from; out of; since; at; on; except; but; other than; more

若い (わかい)

young; youthful; immature; green; low (number); small

丈 (だけ)

only; just; merely; simply; no more than; nothing but; alone; as (e.g. as soon as, as much as); worth

です (です)

be; is

Readings: ヒ、かれ、かの、か.の

Meanings: he, that, the

Readings: サイ、セイ、とし、とせ、よわい

Meanings: year-end, age, occasion, opportunity

Readings: ボク、しもべ

Meanings: me, I (male)

Readings: ジャク、ニャク、ニャ、わか.い、わか-、も.しくわ、も.し、も.しくは、ごと.し

Meanings: young, if, perhaps, possibly, low number, immature