private void requestParentBlock(final Block block) {
    final BlockHeader blockHeader = block.getHeader();
    if (processingBlocksManager.addRequestedBlock(blockHeader.getParentHash())) {
      retrieveParentBlock(blockHeader);
    } else {
      LOG.debug("Parent block with hash {} is already requested", blockHeader.getParentHash());
    }
  }
Process pending Children if any

@param block the block to process the children
@return true if block has any pending child
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/BlockPropagationManager.java