Take a continuous-time Galton-Watson tree and pick $k$ distinct particles uniformly from those alive at a time $T$. What does their genealogical tree look like? The case $k=2$ has been studied by several authors, and the near-critical asymptotics for general $k$ appear in Harris, Johnston and Roberts (2018) . Here we give the full picture.
"The genealogy of Galton-Watson trees." Electron. J. Probab. 24 1 - 35, 2019. https://doi.org/10.1214/19-EJP355