\begin{table}
\centering
\begin{tblr}[         %% tabularray outer open
]                     %% tabularray outer close
{                     %% tabularray inner open
colspec={Q[]Q[]Q[]Q[]},
hline{2}={4}{solid, black, 0.05em},
hline{3}={1-4}{solid, black, 0.05em},
hline{2}={3}{solid, black, 0.05em, l=-0.5},
hline{1}={1-4}{solid, black, 0.1em},
hline{4}={1-4}{solid, black, 0.1em},
cell{1}{1}={c=2}{halign=c},
cell{1}{2}={}{halign=c},
cell{1}{3}={c=2}{halign=c},
cell{1}{4}={}{halign=c},
}                     %% tabularray inner close
a &  & a &  \\
sub1 & sub2 & sub1 & sub2 \\
1 & 2 & 3 & 4 \\
\end{tblr}
\end{table} 
