Telegram is arguably the closest there is to an alternative to Whatsapp. Multi-platform and fully featured, its latest update for Android and iOS introduces support for multiple accounts, among several other improvements.
The new chat oriented Skype Preview is available to download for Windows, macOS and Android, offering new features like @mentions, message reactions, new notification panel, new chat media gallery and enhanced group calls.
The latest version of Telegram offers your regular serving of bug fixes, a couple of new features and improvements -- especially on Android. The most interesting of the latter is the new ability to unsend any weird or regrettable messages you might have shared in the last 48 hours. Telegram is multi-platform and available for download here for Windows, macOS, Android, iPhone, and more.
Instant messaging is an increasingly competitive market and despite your best efforts to keep it simple, it's hard to avoid keeping two or three apps around to keep in touch with different groups of people. If this sounds familiar there are a handful of all in one messaging clients that can make things more convenient by keeping all your chats under one roof.