The wording here is really bad and ambiguous, but the answer to this puzzle is that if
- the son inherits $4/7$ of the estate,
- the wife inherits $2/7$ of the estate, and
- the daughter inherits $1/7$ of the estate,
the proportions between wife-son ($1:2$) and wife-daughter ($2:1$) will still hold.
To find these values, translate the problem into equations: we want the wife to have two-thirds of what the wife and daughter share, and one-third of what the wife and son share. Also, the sum of their shares should obviously be $1$, i.e. everything. Altogether we have
$$\begin{cases}w = \frac 23 (w + d) \\ w = \frac 13 (w + s) \\ w+s+d = 1\end{cases} \iff \begin{cases}\frac 12 w = d \\ 2 w = s \\ w+s+d = 1\end{cases}$$
Plugging the 1st and 2nd equations into the third gives us $w + 2w + \frac 12 w = 1$, or $\frac 72 w = 1$, which means $w = \frac 27$. From there we can use the remaining equations to find $s$ and $d$.