# Event study by Kleven

I was reading the following paper by Henrik Kleven et al.

$$ln(w_{ist})=\sum_{j\neq -1}\alpha_{j}I[j=t]+\sum_{k}\beta_{k}I[k=age_{is}]+\sum_{y}\gamma_{y}I[y=s]+\varepsilon_{ist}$$
$$i$$, $$s$$, and $$t$$ denote individual, year, and event time. $$j=0$$ is the first year an individual has a baby. $$\beta$$ and $$\gamma$$ indicate age dummies and year dummies. Event time dummies $$\alpha_{j}$$ captures the causal effect of having a baby on wage.
This is a silly question. Is it possible to control for individual fixed effect $$\sum_{x}\delta_{x}I[x=i]$$ after controlling for event time dummy, age dummy, and year dummy? Technically it will be possible, but does it make sense? My instinct is that it should not be included. There must be a reason why it is not controlled. But I can't understand why.