The assassination of Commodus in 193 AD caused the Roman Empire to go through a chaotic period of assassination and civil strife known as the Year of the Five Emperors. After the initial successor, Pertinax was assassinated by the praetorians, the office of emperor was auctioned off to Didius Julianus for a huge payment to each Praetorain. This move sparked off challenges from three provincial governors, Pescanius Niger in Syria, Clodius Albinus in Britain and Septimius Severus in Pannonia. Severus being closest reached Rome quickest, deposing and executing Julianus.
To prevent himself from being caught in a two front war, Severus then offered the title of Caesar and the de facto position of heir apparent to Clodius Albinus. Albinus accepted largely because he didn't personally aspire to be emperor at that point. With his rear secure, Severus went on to defeat Niger at Issus in 194. IOTL Severus then decided to double cross Albinus and declared his sons Caracalla and Geta co-emperors instead. This lead to Albinus crossing over to Europe in an attempt on the throne but he was soundly defeated at the Battle of Lugdunum.
WI Severus never had a male heir ? Would he have back stabbed Albinus if he hadn't had a chance of passing down his position to his children ? Would a Roman Empire which didn't have to go through the troubled years of the Severan Dynasty be vulnerable to an almost complete collapse like the OTL's Crisis of the Third Century?