When copying from 𝓞 into 𝓟, Oliver Cowdery initially wrote “the sons and the daughters” after behold. The occurrence twice of the definite article the is undoubtedly the result of anticipating the immediately following relative clause (“which are the sons and the daughters of my second son”). Oliver’s two corrections of the to my appear to be nearly immediate; although supralinearly inserted, there is no change in the level of ink flow. Oliver’s corrected text in 𝓟 undoubtedly follows the reading of the original manuscript (which is not extant here). Note, in particular, the precise parallelism of this passage with the one in verse 3 (“behold my sons and my daughters which are the sons and the daughters of my first born”).
Summary: Maintain in 2 Nephi 4:9 the corrected text in 𝓟 (“behold my sons and my daughters”).