AFAIK you do not need multiple VPNs to connect multiple VPCs. One VPN in each VPC, configured to route accordingly should work. Here is an article with details. See the section "Connecting Additional VPCs"
https://aws.amazon.com/articles/0639686206802544
Unfortunately in order to peer, the VPCs must be in the same region, so peering will not work. Connecting VPCs in different regions is a little more compacted. Here is a link to an article that talks about the different options. The best solutions require some kind of VPN through a corporate network.
https://aws.amazon.com/answers/networking/aws-multiple-region-multi-vpc-connectivity/
Here is the software solution from the article. Of interest, "Ocedo AutoVPN currently provides advanced network automation for launching, managing, and configuring software-based VPN appliances to connect multiple VPCs and full-mesh VPN networks."
Software VPN Appliances
This approach leverages the Amazon VPC capability to create VPN tunnels between EC2 instances in order to route traffic between VPCs in different regions. This option uses customer- or AWS Partner Network (APN) member-managed, EC2-based software VPN appliances and is best suited to customers who want to manage both ends of VPN connections using their preferred VPN software provider.
This design optimizes cross-region network transfer costs, however it requires customers to design and manage their own HA configuration for EC2 network instances.
Configuration Details
This design uses Elastic IP addresses and VPC Internet gateways to facilitate communication between the software VPN appliances. Although EC2 instances are configured with public IP addresses, network traffic between AWS Regions traverse the AWS global network backbone by default, which typically provide more consistent, lower latency network connectivity than equivalent Internet-based connections. AWS Marketplace provides multiple third-party and open source options (including products from Cisco, Fortinet, Ocedo, OpenSWAN, OpenVPN, Palo Alto Networks, Sophos, and Vyatta) for implementing software VPN appliances. Ocedo AutoVPN currently provides advanced network automation for launching, managing, and configuring software-based VPN appliances to connect multiple VPCs and full-mesh VPN networks.
Considerations
Products available in the AWS Marketplace provide additional network control features for monitoring and controlling traffic between VPCs. These include additional security features such as enhanced monitoring, network-protocol-aware firewall rules, or universal threat management capabilities. Note that customers must run network appliances in each VPC, which results in additional EC2 and, potentially, third-party license charges. These EC2 instances can also introduce a single point of failure into the network architecture, and a potential network bottleneck, so be sure to choose a VPN appliance instance size that will meet cross-region network routing requirements. Finally, leverage Auto Recovery for EC2 or other network monitoring and recovery options to decrease the time to recover failed VPN appliances.
